Hydraulic fracturing is the injection, under pressure, of water, sand, and/or other fluids within a well formation to induce fractures in a rock layer. Oil and gas drilling operators commonly use hydraulic fracturing, or “fracking” to release petroleum and natural gas well as other substances from the rock layer. The high pressure injection creates new channels in the rock which can increase the extraction rates and ultimate recovery of fossil fuels. A hydraulic fracturing pump or “frac pump” is used to pump water, sand, gravel, acids, proprietary liquids and concrete into the well formation. The solids pumped down the hole into the fractures keep the fractures from closing after the pressure is released. Operators generally attempt to pump as much volume as possible at or above the pressure necessary to frac the well.
Fracking gas or oil wells is very expensive and generally charged by the hour. Because the formation may be located thousands of feet below the earth's surface, the pressures generated and required by frac pumps are substantial, sometimes exceeding 20,000 pounds per square inch (psi). At peak times, a given frac pump may operate for more than eight consecutive hours (with drive engines running) at as much as 2800 revolutions per minute (rpm). With gear changes, the pump generally runs between a low of 60 rpm to a high of as much as 300 rpm.
A frac pump comprises two major components: a power frame and a fluid end. The power frame and fluid end are held together by a group of stay rods. The power frame is driven by high horsepower diesel engines, electric motors, or turbine engines. Internally, a frac pump increases pressure within a fluid cylinder by reciprocating a plunger longitudinally within the fluid end cylinder. Conventional high pressure, high volume frac pumps have either three or five cylinders. Other designs may have more or fewer cylinder counts.
The fluid ends of hydraulic or well stimulation pumps must produce enormous pressure and move a large volume of abrasive fluids that is high in solids content. Frac pumps were originally designed for intermittent service of six to eight hours per day. Today's pumps operate many more hours per day, and require much more maintenance than ever before.
A conventional fluid end comprises a block of steel comprising a plunger opening and compression area, intake and pressure vales with an intake path for supply of media to the plunger area and an exit path, internally connected to the compression chamber, for the pressurized fluid transfer. The vast majority of conventional frac pump fluid ends are “mono blocks”. A mono block is machined from a single piece of material weighing approximately 4500-8000 lbs. Recently, segmented fluid ends have been introduced in which the block is divided into a number of pieces corresponding to the number of cylinders. For example, a three cylinder fluid end (“triplex”) in such a conventional segmented fluid end comprises three segments and a five cylinder fluid end “quint” comprises five segments. Each segment of such segmented fluid ends comprises a single block of material. The design and maintenance of the conventional one piece segmented fluid end is virtually no different than the design or maintenance of the conventional mono block.
After extended periods of use all fluid ends, either mono block or one piece segmented head, become worn or cracked and have many hours of downtime due to the many pressure and intake valve changes through the life of the one piece construction of the fluid ends.
Maintenance demand of the mono block or solid block segmented head design produces a great deal of downtime. Loss of a single cylinder of the mono block or one piece segmented head requires a complete replacement at great financial cost. Maintenance and repair creates machine downtime and increases the overall cost of oil and gas production. In order to repair a conventional mono block fluid end, the fracking trailer must be transported to a repair facility and the entire fluid end (mono block or solid piece segmented fluid end) must be removed from the pump with overhead cranes or fork lifts, disassembled, repaired or replaced. No disassembly of the one piece segmented head assembly can be performed in the field. The entire assembly has to be removed, no different than the mono block, because of design and weight. Only valve changes, plunger and packing changes can be performed in the field. Even with conventional segmented fluid ends, repairing a failed segment requires disassembly of the entire fluid end assembly, removing the affected segment comprising the plunger, one piece segment, intake valve, pressure valve and rear access discharge cover. This rear cover gives the required access, of the mono block or one piece segmented fluid end, to the intake valve, seat, valve spring and can hold the intake valve spring retainer. The segmented head of the present disclosure does not have or require the use of the cover, spring retainer or access point for the installation or service of the intake head. With the existing segmented designs, the loss of the intake or pressure valve or a worn or cracked manifold area requires the replacement of the entire segment. Valve changes in existing segmented fluid ends are no different in terms of actual time or method of replacement, than in a mono block. Such repair activities are costly and time consuming.
Due to the long rebuild turnaround, operation under less than ideal conditions, and high maintenance costs, frac pump owners inevitably must “over-buy” fracking units (at a cost of millions of dollars per unit) to compensate for the number of pumps that are constantly out of service.
What is needed is a fluid end that can be easily and cost effectively manufactured, serviced, and maintained preferably in the field.
The present disclosure provides a segmented fluid end comprising interchangeable plunger portions, intake portions, and pressure head portions such that the fluid end may be easily manufactured, and be quickly, easily serviced, and repaired in the field or service center.